Physics for IGCSE & O level - Forces And Motion (Section 11 - No. 29)
Which of the following statements are true regarding friction?
Friction always acts in the direction of the motion.
Friction is a force that opposes motion.
Friction depends on the nature of the surfaces in contact.
Friction only exists between solid objects.
Paliwanag
Friction opposes motion and is related to the surface properties.